1. Field of the Invention
The invention relates to viewports for high temperature furnaces and in particular to such ports that provide minimum thermal disturbance.
2. Description of the Prior Art
Viewing ports for furnaces and ovens have been common for adjusting flames and for observing work in progress. Open ports and ports covered with heat resistance glass or quartz have been used. It has also been known to use photographic and video cameras to observe explosions and heating action.
Any hole or penetration into a heated cavity produces thermal distortions of the heat flow within. Such distortion can be extremely detrimental in, for example, growing monocrystal material for integrated circuit use. At the same time, observation can be very desirable in order to control temperatures in accordance with the activity. Prior viewports have not overcome this problem.